Jumbo Frames on Cisco 3750 stack

Posted on 2009-05-22
Medium Priority
Last Modified: 2012-05-07
We have a stack of four Cisco 3750 switches that handle all network traffic, including internet routers (10mbps), firewalls (10/100), internal servers (1000) and iSCSI.

Two questions regarding enabling Jumbo Frames for the iSCSI traffic:

1. Since the 3750 switches requires that Jumbo Frames be configured for all gig ports, does that mean that configuring it on the stack will set it for all switches? Or can I configure Jumbo Frames on two of the four switches only?

2. If Jumbo Frames are configured on all ports, will this affect traffic between devices not configured for Jumbo? For example, if my iSCSI VLAN is the only VLAN using Jumbo (and all devices on it are properly configured for Jumbo), will devices on the other VLANs be affected, assuming nothing else changes? Or do I need a switch outside of the stack dedicated to iSCSI in order to use Jumbo Frames?
Question by:CommunispaceIT05
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Accepted Solution

Don Johnston earned 750 total points
ID: 24451178
The global command will apply to all interfaces on all switches in the stack.

Expert Comment

ID: 24460450
Think of the stack like a chassis switch as the global config commands controls all ports on all switches.

Author Comment

ID: 24472050
Any comments on point #2?

Will enabling Jumbo Frames across the stack affect traffic on non-Jumbo-enabled devices, keeping in mind that jumbo packets will only be targeted to jumbo-enabled devices.
LVL 50

Assisted Solution

by:Don Johnston
Don Johnston earned 750 total points
ID: 24472089
The answer is no. You are increasing the MAXIMUM frame size. The switch can still process frames down to 64 bytes.

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